1. Field of the Invention
This invention relates to an electrophotographic photosensitive member, and particularly to an electrophotographic photosensitive member having an amorphous deposition layer as a photoconductive layer.
2. Description of the Prior Art
The electrophotographic photosensitive member takes various constructions to obtain predetermined characteristics or in conformity with the electrophotographic process to be adopted. The principal part of this electrophotographic photosenstive member is a photoconductive layer, the performance of which depends largely on the photoconductive layer.
Representative photoconductive layer which has heretofore been known is formed by vacuum-deposition of inorganic photoconductive materials such as S, Se, PbO, or alloys or intermetallic compounds, both of which contain therein S, Se, Te, As, Sb, Pb, etc. While the photoconductive layer formed by the vacuum-deposition has generally high sensitivity and is excellent in mechanical strength, there have been pointed out various problems still to be improved in respect of some of various electrophotographic characteristics. The main point to be improved is the so-called "fatigue phenomenon" which takes place when the photosensitive member is used repeatedly. This fatigue phenomenon is such one that emerges remarkably when the photosensitive member is used repeatedly at high speed. It is recognized from gradual lowering of image contrast in an electrostatic latent image to be formed during repetitive use of the photosensitive member, or from a ghost image to remain on a subsequently formed electrostatic latent image due to the previously formed electrostatic latent image not being completely removed.
For preventing such fatigue phenomenon with the photosensitive member having an insulating layer on its surface, there has so far been proposed in laid-open Japanese Patent Application No. 52-145037 (West German Offenlegungsschrift No. 2723925) a method of temporarily lowering the temperature of a substrate during the deposition, when a photoconductive material is deposited on the substrate to form a photoconductive layer thereon. However, the temporary decrease in the substrate temperature during the deposition requires a deposition apparatus of a complicated construction provided with a cooling device, as the result of which the deposition operation becomes also complicated.